Safety timing switch



p 1952 A. L. JUDSON 2,610,273

SAFETY TIMING SWITCH Filed July 13, 1950 2 SI'iEETS-SHEET 1 uwfwrg ALBERT L. JUDZJON A T'TURNEV Sept. 9, 1952 JUDSON 2,610,273

SAFETY TIMING SWITCH Filed July 13, 1950 2 SHEETS SI-IEET 2 A 7' TERA E Patented Sept. 9, 1952 SAFETY TIMING SWITCH Albert L. Judson, Portland, reg., as'signor to Iron Fireman Manufacturing Company, Portland, Oreg.

Application July 13, 1950, Serial No. 173,616

'9 Claims. 1

This application is a continuation-impart of application S. N. 20,003, filed April 9, 1948, jointly by Lewis L. Cunningham and Albert L. Judson on an Oil Burner Primary Control, which application issued as Patent Number 2,581,636 on January 8, 1952.

I This invention relates generally to thermally actuated electric switches and more particularly to thermally actuated electric switches of the type found useful in Oil Burner Primary Controls for measuring out a limiting time interval during which it is safe to inject oil into the furnace before proper ignition is assured.

To be reliable in time measurement such switches, which rely on an increase of temperature of a bimetal member due to the heat emitted by a fixed resistor through which electric current is passed at a predetermined rate, must be compensated for ambient temperature changes.

It is a common practice in this art to provide a device of this general type having two substantially parallel, spaced bimetal elements of approximately the'same active length and similarly influenced by ambient temperature, with each of the elements having a fixed and a free end and with a bridging member hinged to the free end of one of the elements and resting on the free end of the other bimetal element and wherein the bridging member will be released to open a switch when one of the bimetals is heated to a temperature by an electric heater.

It is a principal object of the present invention to provide an improvement in this generaltype of switch in which the compensating bimetal blade has no structural duty in the switch operating mechanism other than its compensating duty of positioning the bridging member with respect to the other bimetal blade.

How this and other objects are attained will be made clear by reference to the following specification referring to the attached drawings in which Fig. 1 is a view in perspective of the essential elements of one form of my device with the switching bridge member-in switchclosed position.

frame ofthe device of Fig. 5. v ,Fig. '7 isa plan view of the switch opening strut of the device of Fig. 5.

.Fig. 8 issideelevation of the device of Fig.

withjthe elements in they switch open position.

Fig. 9 is the same as Fig. 8 but with the elements shown in position at the time of resetting the device after the switch has been tripped as in Fig. 8.

Fig. 10 is a sectional View taken along the line |0||J of Fig. 8.

Referring now to Figs. 1 to 4 of the drawings, arched bronze leaf spring is supported at its upper end by machine screw 2| threaded into insulating base member 22 and has secured to its downwardly extending end, by machine bolt 23, bimetal element 24 and electric resistor 25 insulated from spring 20 by fiber insulating strip 26. Due to the arched formation of the upper end of spring 20 the lower end of bimetal 24 is moved to the left by tightening screw 2| or to the right by loosening screw 2|.

Secured to stationary brass bracket 21 by screw 23 and spacer 29 are bronze spring 30 and bimetal 3|. Insulating strip 32 has its right hand end biased upwardly by spring leaf 30 to which it is secured by conducting rivet 33 which in the position shown in Fig. 1 makes electrical contact with conducting rivet 34 securing stiff metal conducting bridge member 35 to bronze leaf spring 36 having its right hand end secured to strip 32 by hollow rivet 31. Spring 36 biases the left hand end of bridge 35 downwardly as shown in Fig. 2 when the right hand end of bridge 35 is unlatched from bimetal 24 as bimetal 24 is warped to the right under the influence of heat emitted from resistor 25 as current is passed therethrough. Double headed loose rivet 38 secured to bridge 35 and T-headed pin 39 limit the movement of bridge 35 with respect to strip 32.

Reset knob 40 secured to crank shaft 4| by pin 42 is used to rotate crank arm 43 downwardly against stop 44 formed on enclosing cover 45 in which shaft 4| is journalled as shown in Fig. 3. Wire spring 46 secured at one end to stationary member 41 biases crank arm 43 upwardly against stop 48 formed on cover 45. Rotating knob 40 to the right causes crank bar 49 to move the right hand end of bridge member downwardly to its reset position as latched on to the end of bimetal 24 as shown in Fig. 1. When arm 43 is in its upper position against stop 48 rod 49 forms a stop limiting the-upward travel of bridge 35 when it is unlatched from bimetal 24.

Tang 53 formed on the lower end of compensating bimetal 3| fits loosely into slot 5i formed into strip 32. The right hand end of slot 5| presses lightly against tang 50 due to a slight leftward bias of spring 30. Shoulders 52 on bimetal 3| limit the upward motion of strip 32 in the position shown in Fig. 2.

Bimetals 24 and 3| warp in the same direction on a temperature change and therefore bridge .35 and the lower ends of bimetals 24 and 3| will 3 maintain their relative positions when influenced only byithe ambient temperature. But when current passes from wire 53 through bracket 21 spring 30, rivets 33, 34, bridge 35, bimetal 24, resistor 25, and wire 54, birnetal 24 is heated by resistor 25 and will warp to the right unlatching bridge 35 and breaking the electric circuit between bimetal 24 and bridge 35 as wellas between rivets 33 and 34. i

Figs. 5 to 10 inclusive illustrate another 'form of my invention in which bracket 60 secured to insulating base 6| by rivets 62 carries throughinsulated rivets 63 an electric resistor insulated from bracket 60 by fiber strips 65, and energizable through-wires .66 and 31..

'r'espeetwery are bronzeiear Spring blades 11 and tiondb'y 'adjustifig serew .18: journalld loosely in base '61 ,ar idt tliiaiddl into rame Strained between; fame; 1.11am stiff bridge member I9,coil sprihgtll'bia'ses bridge member "19 to.iotate. iii acoliiitfclokwise direction about its owemna rdc amyi, e gaged with one end of fia rhfstrut'. Theiothef fid of strut 8| is rockablylpivotfl oii fra e vThe free .end of compensating, bimetal 18 against the lower edge or east foriiid iii frame'striut '8! as shown and. gent y resists the, eountrei c wise biasin action orsbi-ingso'on' StilifiBTwith res ect to frame.1'1.,,. v v

Switchopening stiiit'BZ isfnade of insulating material and has al s iiigl step, shoulderediedue'ed p ftion at dnend resting in a slot formed in bridge 1191 and limitingfthe counterclockwise rotation 'ofjbii d ge 19. At it other n trut s2 is, first r duced, inwidth and [shouldered to pass an'nnteataistaneet ron s a slot formed in base B If anda'second'slot formed in switch blade [2 as showni'ri Fig. 7. After passing through base 6], andbladelZ. strut 82 isagain vreduced and 'sli'ould'e'redwithjits" secondreducedfportion passingjt'hrough a slot formed in blade'll and with its second shouldersetting'. a spread between bridge 19 ahdblade' 'I l. It isseen, as in ig.5.. that fit the me end or bridgeje is latched or' thefr'ee end ofbimetal a3 riveted to bracket 60.,the biasing actioniof switch'blade H will push. strut82 to thefrightl for enough to allowcontac'ts 39 and 1.0 to close but if bimetal 83 .warpsi upwardly enough to anew bridge 19 to be unlatched, therefiohr then. pring, 80, through bridge 19.2.1161 Slil'lltflZ will pushblade 12 to'the 'left and open contacts 6 9', |0. The switch opening action of strut 82 isliin'ited by its shoulder formed where the strutis' reduced-in width to passthroughl base 5|,

Resetting'strut 84 also made drumming material is guidedat it"s'jfull width towards one end in slot 'asro ma'm irameJT and at its other end is shouldredian'd reduced in' width to pass through and bejg'uidjed in a'slot formed in base Bl as shown. The'jshouldr thusforrried coacting with ba'sefiijliniits tliefrn lenient of strutB l t0 the "left; Th'iedued portion Of Str ut 84 is ed on by outside forces.

- the ambient temperature onthejrelati "c sine-i1 tri'calfheater on firs 4 notched on its opposite edges as shown at 86 to receive the bifurcated end of switch blade 12 which being of ifspring' naterial biasingjits contact end to the neutral position shown in Fig. 8 locates strut 84 in its endwise position unless act- 7 H Thus should bridge 19 be unlatched from bimetal 83 and switch contacts 69 and lube opened as shown in Fig. 8,

smarter bi mtaljtii has cooled, it is desired to reset the fdevi c e the left end of strut 84 can base- 61 which would be the limit of motion to the right for strut 84. In this position the end of bridge 19 would be; well beyond the end of closed position-by manipulationoi H r 84. A carefulexamination of th dra', ng ll show that' switchlcontacts 59 10 r g c d Po o he"br d e issia i m tal 8 3 6 'r's fi ne'. 'Stri .84 gf Si On' -b blade 72 which in its neutral "pb'sition'j W111i contacts se 1u'toe1o e w11fe r bri g'e 'l 9allovvs blade H to push trut 2 t t" V In the form oifthef 'dev e" to 0 the switch an'd'joper'atifi ;r connected n ser esafter the shown in Figs rand 7 w be mi e to .611 are and 6? and the switch another oircuitfthroug'hter J I Having thus; completely di losefafnd described t o forj jofmyimproy d r lay n w i 1 .5 o h w a fil b1 has no runetionegqepptonegate he 11 of the bridge and the otherfbimetal; I'claizni 1 1i In a p maryt ntro r a if il b said switch and ber is used to j n i e iceofth of said tWo bi -meta m wherein sai b; s ef' 'n an. additional. Ir ilient"ibiasirig 4 wherein Saidbr'idging member is located w v spect to said first oi-metal member by said second "member is biased by sa d biasing member. I

2; In a rimary comforter 'ar'i'oil burnen a safety timing switching means comprising a first bi-metaljelefiieritj a second bi al" element, means bridg'ingfthef freeefi second bi metal eleirients', a u ju lrfi ngo -feiid to said support," means for fixing'one end "0' aid Second e a e e t to said suppo t. independentof'saidfbi ably carrying saidb' dgiiig'fn port, means forbiasi ment is influenced by said second bi-metal element.

3. In a primary control for an oil burner, a safety timing means comprising a support, a first bi-metal element having one end adjustably fixed to said support, a second bi-metal element having one end fixed to said support, a bridging means, means flexibly carrying said bridging means on said support and resilient means adapted to bias said bridging means against the free end of one of said bi-metal elements in its temperature responsive direction and against the free end of the other of said bi-metal elements in a, direction perpendicular to its temperature responsive direction.

4. A thermostatic time switch comprising in combination, a first bi-metallic blade fixed at one end to a support and free at the other end, a second bi-metallic blade fixed at one end to said support and free at the other, said blades being adapted to warp in the same direction on a change in ambient temperature, a third blade rockably carried on said support in substantial parallelism with one of said bi-metallic blades, means operably connecting the freely rockable end of said third blade with the free end of said second blade for movement therewith, a lever fulcrumed on said freely rockable end of said third blade, means rotatably biasing one end of said lever against the free end of said first blade in the direction of the fixed end of said first blade, a normally closed electric circuit opening means, means adapted to raise the temperature of one of said bi-metallic blades a substantial amount above the ambient temperature in a fixed time period, whereby said first blade will release said lever at the end of said period, and means whereby said circuit opening means is moved to open circuit position when said lever is released by said first blade.

5. The device of claim 4 including a screw connection between said first blade and said support for adjusting the position of the free end of said first blade with respect to the free end of said second blade.

6. The device of claim 4 including a manually operable push rod adapted to engage said lever for returning said lever to its latched position on said first blade after having been released therefrom.

'7. The device of claim 6 including means formed on said push rod-adapted to engage said circuit opening means for maintaining said circuit opening means in open circuit position during the manipulation of said manual means.

8. A thermostatic time switch comprising in combination, a first bi-metallic blade fixed at one end and free at the other end, a second bimetallic blade fixed at one end and free at the other end, said blades being so arranged that their free ends move in the same direction on temperature variations to which they are similarly subjected, a third blade rockable in substantial parallelism with said second bi-metallic blade, means operably connecting said third blade with said second bi-metallic blade for movement therewith, a latching means pivotally carried at one end on said rockable blade and normally latched on the free end of said first bi-metallic blade, an electric heater for one of said blades causing it to warp in a direction to release said latch, and a pair of electric switch contacts normally biased to closed position and adapted to be moved to open position on the release of said latch.

9. A thermostatic switch comprising in combination, first and second bi-metallic blades fixed at one end and free at the other, a rockable blade, a latching means pivotally carried at one end on said rockable blade and normally latching on the free end of said first bi-metallie blade, means operably connecting said latching means with the free end of said second bi-metallic blade whereby a lateral movement of said second bi-metallic blade will cause an equivalent longitudinal movement of said latching means, means for causing one of said bi-metallic blades to move away from the other of said bi-metallic blades whereby said latch will be released from its latched position on the free end of said first bi-metallic blade, a pair of electric switch contacts biased to a closed contact position, and means operatively connecting said latching means and said switch contacts whereby when said latch is released from the end of said first bimetallic blade said contacts will be separated.

ALBERT L. J UDSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,725,518 Hodgkins Aug. 20, 1929 2,235,337 Shaw Mar. 18, 1941 2,290,399 Wilson July 21, 1942 2,581,636 Cunningham et al. Jan. 8, 1952 

